Just an update if anyone is interested, made a start on the custom gear - found an old plastic screwdriver and cut it into shape, atm it is almost the perfect size, just need to cut in the 20T and it will be tested. If it is successful then I'll make a 10T for the front in the same way.

I'll make a tutorial for the next custom gear as I forgot to take any pictures of this one.

I only was able to carry on with the custom gear today. I had the shape all done, but when it came to marking up the teeth and cutting it they weren't cut perfect so I ended up binning it and will start over again.

This time I will make a guide step by step, may make it from a block of aluminium but I don't know if that will shred the standard diff gears? Otherwise I'll make it from plastic.

Will keep you updated, if you want more info PM me and I'll give you my email.